Disk defragmenting is unnecessary and not recommended for a solid-state drive.

Since my last post about how solid-state drives are the wave of the future (which means you should get one now, by the way), I've received a number of questions about the disadvantages of this new and superfast type of internal storage, apart from the high prices.

Well, here goes: All NAND flash-based solid-state drives, which are the majority of SSDs on the market, have a finite time of writing, called "write endurance rating." In other words, an SSD can be written on a limited number of times before it becomes unreliable. Of course, before you can rewrite on a part of the drive, you'll need to first erase information already stored on that part. This is why the write endurance rating is also known as the P/E cycle, or program/erase cycle.

It would be impossible to explain P/E cycles in detail without using technical jargon, but basically, flash cells wear out each time you write to them. In a way this is very similar to writing on a piece of paper using a pencil and an eraser. You can only erase the pigment so many times before the piece of paper becomes worn out or even torn and can't be written on anymore.

Now, before you let out a "D'oh!" and return your beloved recently purchased SSD, be aware that the number of potential P/E cycles for an SSD is much larger than that of paper. On top of that, modern SSDs have technologies that increase the efficiency of writing and reduce wear on its storage cells. Among these technologies, the most important are the "wear-leveling" algorithms that effectively make sure that all the drive's memory chips are used up, cell by cell, before the first cell can be written on again. This also means that SSDs of larger capacities generally have a longer life span than smaller ones.

So how long is long To help users estimate how long an SSD will last, SSD vendors such as OCZ have come up with formula: a drive's life span equals its capacity multiplied by its write endurance rating, divided by the average daily writes. For example, the 120GB Vertex 3 SSD has a write endurance rating of 3,000 cycles. If you write 50GB on the drive daily, the total number of days the drive will last before becoming unreliable is: (120 x 3,000)/50 = 7,200 days, which is about 20 years. If you write an average of 100GB a day, the drive would last about 10 years.

Most of us actually write much less than 50GB of data, which is about two Blu-ray disks' worth of data, on our computer's host drive on a daily basis, and many days we don't write anything at all. Note that watching movies, reading PDF files, or viewing photos doesn't count as writing' that's reading, which has no effect on an SSD's life expectancy. Activities like copying music from another drive, downloading files, or backing up your phone do require writing to the drive.

To maximize the life span of an SSD, apart from making an effort to reduce unnecessary file copying, downloading data onto the drive, and so on, you should note that there are a few settings of the operating system as well as common tasks designed for regular hard drives that shouldn't be used with SSDs. On Windows 7 computers, these include:

(Note that these are just precautions' if you use an SSD the way you would a hard drive, chances are it will still last longer than a regular hard drive would.)

It's good to turn off hibernation on a computer that uses an SSD as its main drive.

Defragmentation: On hard drives, information stored on the outer part of the platter can generally be accessed faster than information stored on the inner part (the part close to the middle of the platter). This is because physically, like a wheel, the platter moves faster farther away from the spindle. For this reason, defragmentation, a process that reorganizes data by moving it toward the outer part of the platter and putting files in contiguous regions, helps improve a hard drive's performance.

On an SSD, however, as there are no moving parts, information stored on the drive is equally accessible regardless of its location on the drive. This means defragmentation is unnecessary. And as defragmenting basically means moving data from one place to another, it helps use up the drive's P/E cycles.

Windows 7 supports SSDs natively and automatically excludes them from the list of drives that are defragmented on a schedule. To be sure, however, you can turn off the scheduled defragmentation by running a program called Disk Defragmenter (it can be found in the Start Menu) and clicking on Configure Schedule. The rest is self-explanatory. And, of course, refrain from running defragmentation on an SSD manually.

Benchmarking: Most of us want to find out just how fast our new SSD is, and when we have one we just can't wait to test it out by copying files from one place to another or using disk benchmarking software. While this is fun and the information is useful to know, it wastes the drive's P/E cycles. Next time you have the urge to do it on your SSD, just turn to CNET, where we do most of the benchmarking so that you don't have to.

It's best to use AHCI when using an SSD as a single volume.

Hibernation: This is a feature found in most operating systems in which the contents of system memory (where running programs and information being processed reside) are written to the computer's internal storage device before the computer is powered off. When the computer is restarted, the system reloads the saved contents back into the system memory, and hence restores the computer to the state it was in before it was turned off. Once the loading is completed, the saved contents will be deleted from the storage.

As you can imagine, depending on the amount of system memory, the hibernation process can use gigabytes of storage space, which translates into a large amount of writing on the internal storage. And when an SSD is used, that's not a good thing. So when you use a computer with an SSD, try to avoid using hibernation. Sometimes the computer goes into hibernation by itself, but you can avoid this by completely turning off the hibernation function. Here is how:

On the Start Menu, look for "Command Prompt," then right-click on it and choose "Run as administrator," and answer yes to the User Account Control security prompt. (By the way, this is called running "elevated Command Prompt"' note it down, as you'll need it often). When the Command Prompt window appears, type in powercfg -h off and then press enter. That's it' your computer will never go into hibernation mode again. To turn this feature back on, repeat this process and type powercfg -h on.

A computer that's equipped with an SSD generally boots really quickly, so you can always just save your work and turn it off. Avoiding hibernation also helps the system to run well and error-free.

The TRIM command enhances the performance of SSDs with Windows 7.

AHCI and TRIM commands: AHCI, which stands for advanced host controller interface, allows the operating system to access the storage faster and use advanced functions. One of these functions is the TRIM command, which allows a supported operating system, such as Windows 7, to actively inform an SSD which blocks of data are no longer considered in use and can be wiped internally. This helps the drive work more efficiently and leads to faster performance.

Generally, both AHCI and TRIM are enabled by default. You can check and change the former in the computer's BIOS setting. It varies between computers but with most computers you can enter the BIOS by tapping on the Delete or F2 key as the computer boots up. Here, look for the storage section and change the value of "Configure SATA as" to "AHCI" (if it's not already AHCI). It's better to do this before you install the operating system, as otherwise you'll need to install the storage drivers first before changing the value. Note that if you use two SSDs in a RAID configuration, then the RAID value should be selected.

For the TRIM command, you can check if it's running by running elevated Command Prompt as described above, then executing this command: fsutil behavior query DisableDeleteNotify. If the command returns "DisableDeleteNotify = 0" then TRIM is running. If not, you can turn it on by executing fsutil behavior set disabledeletenotify 0.

Page File (aka virtual memory): In an operating system like Windows 7, the Page File could be seen as a system memory wannabe. In a nutshell, this is the amount of storage space on an internal storage device that the operating system reserves for use when an application requires more memory than the computer is equipped with. The Page File's size tends to change dynamically and this means lots of writing to the drive, which is, again, not good for an SSD. So if you use a laptop with 4GB of memory or more, it might be a good idea to turn off Page File completely, or at least reduce it to a fixed size of around 300MB. If you run a desktop that has a hard drive as a secondary drive, it's best to move the Page File to the hard drive and not have it on the SSD.

To change the setting of Windows 7's Page File, follow these steps: Run elevated Command Prompt and execute control sysdm.cpl command. Now as the System Properties window appears, pick the "Advanced" tab and click on the first "Settings..." button. The Performance Options window will appear. Now click on its "Advanced" tab, then click on the "Change" button. The rest is self-explanatory.

Turning off Page File on an SSD helps extend its life span.

There you go' after all that, you can rest assured that you've done most of what can be done to keep your SSD long-lasting. Again, note that these are just precautions. Also, the most important thing you can do is restrict the amount of writing on the drive.

The truth is SSDs and operating systems all come with methods of reducing unnecessary writing. So for most of us, we can just enjoy the superfast speed and don't have to worry at all.